Mercury dangers: Real and imagined

From: 	Eric Davidson[SMTP:edavidson-at-icva.gov]
Sent: 	Tuesday, December 02, 1997 10:31 AM
To: 	Tesla List
Subject: 	Mercury dangers: Real and imagined

Hi All!

Just thought I'd offer my 2 cents worth about mercury. Mercury in its
LIQUID form is not as toxic as many people imagine. Mercury is not very
reactive either (an amalgam is not a reaction with mercury but a
solution of a metal in mercury, just as salt dissolves in water). Silver
and gold amalgams have been used in dental fillings for quite some time
with no evidence of acute toxicity and the chronic sensitivity issue has
not been fully characterized and consists of a lot of anecdotal
evidence. I have known people who have swallowed mercury from a broken
thermometer with no ill effects. The metal simply doesn't react that
easily and passes on through. On the other hand, soluble mercury
compounds are very toxic and are readily absorbed by the body. Most
insidious of all are the volatile organomercury compounds (methyl
mercury for example) they are very toxic and very dangerous to handle.
These types of compounds should never be 'played with', as they are
dangerous to handle even in a proper laboratory. The good thing is that
us Tesla coilers, at least 99.9% of us, will never come in contact with
these compounds. Last of all is mercury in its gaseous (vapor) form.
There is no doubt that mercury vapor is toxic. The issue is: how much
vapor is really in the air? Mercury has an extremely low vapor pressure,
this is what allows it to be used in vacuum gauges without boiling away.
It does slowly evaporate however. The amount of vapor that gets into the
air is related to the temperature, pressure and the surface area
exposed. It is the latter that is the important variable. A tiny pea
sized drop of mercury rolling around on a table or in a beaker is really
pretty harmless. It doesn't have that much surface area. Now lets let it
fall off the table onto the floor. When it hits the floor it splatters
into thousands of microdroplets, multiplying its surface area by maybe a
thousand, and making it almost impossible to clean up. At this point
forget about powdered zinc or copper, its in every little crack and
crevice in the floor. There, it will slowly evaporate over the course of
months and likely, years. So, even though it doesn't evaporate that
quickly, if the spill is in your house you will be breathing a little
bit every day until you move, not good. My advice is to USE and STORE
all mercury OUTSIDE your house, a detached garage is nice. If there is a
spill, clean up what you can and don't worry about the rest, it will
evaporate over the months and years. DO NOT use any household cleaners
to clean a mercury spill, many will react with the mercury forming toxic
soluble compounds. Use powdered Zn or Cu to amalgamate or powdered
sulfur. Most experiments only require a drop of mercury at most, so
don't have much more than that on hand (if you don't have it you can't
spill it!). Do not heat mercury or use it in any 'spark gap' type
situations where arcing could occur, as this will generate alot of
vapor. I am not advocating a lack of safety precautions, its just that a
drop or two of mercury, handled responsibly and knowledgeably, is not
that dangerous.